In recent years, liquid crystal display devices using a liquid crystal display panel and plasma display devices using a plasma display panel (hereinafter simply referred to as a PDP) have been gaining attention as display devices suitable for achieving a reduction in thickness and an increase in size. These display devices have been produced in large quantities and sales thereof also have been increasing rapidly.
The PDP is composed of a pair of panels, a front panel and a back panel, each having a glass substrate. The front panel includes a front glass substrate on which a display electrode pair, a dielectric layer, a protective layer, etc. are formed. On the other hand, the back panel includes a back glass substrate on which a data electrode, a barrier rib, a phosphor layer, etc. are formed. The front panel and the back panel are disposed facing each other so that a minute discharge space is formed therebetween. A gap between a peripheral portion of the front panel and a peripheral portion of the back panel is sealed with a sealing material. The discharge space is filled with a discharge gas containing neon (Ne), xenon (Xe), etc.
A chassis member is attached to a back surface of the back panel of the PDP via a joining member such as an adhesive heat-conducting sheet and an adhesive agent, etc. A peripheral portion of the chassis member is fixed to a mounting metal piece with screws. The chassis member is a substrate for supporting the PDP and attaching thereto circuit boards on which a drive circuit for driving the PDP is formed. The chassis member also has a function of radiating effectively the heat generated by the PDP. Furthermore, the plasma display device includes a front frame and a back cover for protecting the PDP and the circuit boards. On a front side of the PDP, a front protective glass substrate is disposed spaced apart from a surface of the front panel of the PDP. The front protective glass substrate is attached to a front housing portion having an opening corresponding to an effective display region of the front panel of the PDP. The front protective glass substrate has functions of color tone correction, contrast improvement, and electromagnetic wave blocking.
In contrast to the back panel fixed by the chassis member, the front panel merely is fixed, at the peripheral portion thereof, only by a sealed portion composed of the sealing material. Therefore, when the plasma display device drops forward (with the front protective glass substrate facing down) during transportation or unpacking, the front panel is warped in the shape of a bowl taking the sealed portion as the supporting point, and has cracks and fractures.
In order to prevent these cracks and breakage, it can be considered to dispose a frame-shaped elastic member in a gap between the surface of the front panel and the front protective glass substrate along a peripheral portion of the effective display region, as disclosed in JP 2003-131580 A, for example. Such a configuration can enhance the impact resistance of the PDP in a plane direction and block the dust entering from outside. In addition, JP 2003-131580 A discloses to provide an elastic member to a sealed portion.
However, even when the elastic member is provided to the sealed portion serving as the supporting point of the warping as in the technique disclosed in JP 2003-131580 A, the deflection of the front panel itself cannot be suppressed, and thus the occurrence of cracks in the sealed portion cannot be suppressed. The frame-shaped elastic member has an effect of lowering slightly the degree of deflection of the front panel. However, since the elastic member is in contact with the front panel, an initial impact force is applied directly to the sealed portion provided at the peripheral portion of the front panel. This raises a problem in that the distortion is concentrated thereto causing cracks, and the front panel tends to have fractures easily. Moreover, when the elastic member is softened to reduce this initial impact force, the deflection cannot be suppressed.